Flow of electric currents of telluric origin in a long metal pipeline and their effect in relation to corrosion control

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Abstract

To determine the effects of telluric currents on the corrosion of a 280-mile (450-km) steel pipeline in Kenya, Spencer and Partners, London, and the University of Nairobi, Kenya, estimated the extent to which these currents influence corrosion rates on the line, their effects on potential readings, and the possible beneficial effects of further sectioning the lines or installing blocking diodes. Difficulties experienced during the installation of cathodic protection pointed to the presence of stray currents, railway, or various d-c grounds near the pipeline. Data from time-calibrated recording meters and other test information showed that the stray currents correlated with telluric-current magnitudes associated with the sun's activity; sunspot storms were producing currents of up to 2A. Telluric currents substantially affected the accuracy of cathodic-protection tests. This experience validates the contention that coating perfection is helpful, especially in high-conductivity soil zones.